Outline

• What is an API

• The Google Maps API
  • Version
  • Reference Information
  • Key Components
  • Examples

What is an API

• API Stands for Application Programming Interface

An Application Programming Interface (API) is a particular set of rules and specifications that a software program can follow to access and make use of the services and resources provided by another particular software program that implements that API. It serves as an interface between different software programs and facilitates their interaction, similar to the way the user interface facilitates interaction between humans and computers. -- From Wikipedia: http://en.wikipedia.org/wiki/Api

• The Google Maps API provides an interface for interacting with Google’s mapping services from external web applications

Google Maps API Version

• The version of the Google Maps API used in this class is v3 of the Javascript API
  • Freely usable for free applications
  • Subject to Google’s Terms of Service
  • Google API key is optional for our work
• Key capabilities in v3
  • Interactive maps based on Google’s mapping engine (contrast w. static maps API)
  • Optimized for desktop and mobile platforms and applications

Reference Information

Google Maps API Family

http://code.google.com/apis/maps/

Javascript API Home Page

http://code.google.com/apis/maps/documentation/javascript/

Javascript API v3 Tutorial Page

http://code.google.com/apis/maps/documentation/javascript/tutorial.html

Key Components

• Map object options

Types (required)

ROADMAP

SATELLITE

HYBRID

TERRAIN

Latitude and Longitude (required)

specification of where the map should initially be centered

Zoom Level (required)

0=global, higher values increasingly local. Limited by map type

Controls

• Available Controls (enabled through map options) default controls
  • Zoom Control
  • Pan Control
  • Scale Control
  • MapType Control
  • Street View Control
  • Rotate (for maps that contain 45-degree imagery)
• Different control styles may be defined
• Controls may be positioned positioning options
• Custom controls may be defined and attached to fixed location in the map

Overlays

Overlay Types documentation

Marker

points depicted by specified or defined icons at locations within the map

Polyline

linear features defined by multiple points with a defined style for the line

Polygon

closed features defined by multiple points. Supports multi-polygons, and donuts. Line and fill styles may be specified.

(Ground) Overlay Maps

Image-based map layers that replace or overlay Google layers - registered to the map coordinates

Overlays (continued)

Info Windows

floating content windows for displaying content defined as HTML, a DOM element, or text string

Layers

Grouped display content assigned to a specific layer type: Data (including GeoJSON), KmlLayer (& GeoRSS), Heatmap, FusionTablesLayer, TrafficLayer, TransitLayer BicyclingLayer

Custom Overlays

definition of programmatically controlled layers

Services

• Geocoding Service
  • Forward and reverse geocoding:
    • address to LatLon
    • LatLon to Nearest Address
  • May be biased to current viewport, region
• Directions
  • Based upon an origin, destination, and a variety of additional options
  • Available directions and rendered route
• Distance Matrix
  • Travel distance and duration given a specific mode of travel

Services

• Elevation
  • Delivery of elevation data for locations or paths
• Streetview
  • Integration of Google Streetview within a DOM element
• Maximum Zoom
  • Provides information about the maximum available zoom level

Events

• Events provide the ability to attach custom behaviors to events in the interface. For example:
  • Changing items in the interface as the user zooms in on a map
  • Displaying additional information outside the map when the user clicks a location in the map
  • Synchronizing the behavior of multiple maps as the user interacts with one map
• Requires higher-level Javascript than we will cover in this course

Examples

Simple - Roadmap

Simple - Roadmap Code

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<!DOCTYPE html>
<html>
    <head>
        <link rel="stylesheet" type="text/css" href="css/mapPage.css">
    </head>

    <body>
        <h1>Sample Map</h1>
        <div id="map_canvas"></div>

    <!-- Let's put our JavaScript down here --------------------------------------------->
        <!-- Load the external JavaScript file with the map definition code -->
        <script src="js/mapPage_01.js"></script>
        
        <!-- Load the API in asynchronous mode and execute the initialize 
            function when done -->
        <!-- The optional 'key-<API Key>' parameter is not used here but should be 
            for a production map -->
        <script async defer 
            src="https://maps.googleapis.com/maps/api/js?callback=initialize">
        </script>
    </body>
</html>

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/* You must set the height of either the 'html' or 'body' elements for some 
    browsers to properly render the map with a hight taller than 0px */
html { 
    height: 100% }

body { 
    height: 100%; 
    margin: 0px; 
    padding: 0px; 
    background-color: black; 
    color: #CCCCCC;
    text-align: center}
    
#map_canvas { 
    width:90%; 
    height:80%; 
    margin-left:auto; 
    margin-right: auto }
    
.infoBox { 
    color:black }

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function initialize() {
    var classroom = new google.maps.LatLng(35.084280,-106.624073)
    var mapOptions = {
        zoom: 8,
        center: classroom,
        mapTypeId: google.maps.MapTypeId.ROADMAP
    };
    var map = new google.maps.Map(
        document.getElementById("map_canvas"),
        mapOptions);
}

Simple - Satellite

Simple - Satellite Code

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<!DOCTYPE html>
<html>
    <head>
        <link rel="stylesheet" type="text/css" href="css/mapPage.css">
    </head>

    <body>
        <h1>Sample Map</h1>
        <div id="map_canvas"></div>

    <!-- Let's put our JavaScript down here --------------------------------------------->
        <!-- Load the external JavaScript file with the map definition code -->
        <script src="js/mapPage_02.js"></script>
        
        <!-- Load the API in asynchronous mode and execute the initialize 
            function when done -->
        <!-- The optional 'key-<API Key>' parameter is not used here but should be 
            for a production map -->
        <script async defer 
            src="https://maps.googleapis.com/maps/api/js?callback=initialize">
        </script>
    </body>
</html>

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function initialize() {
    var classroom = new google.maps.LatLng(35.084280,-106.624073)
    var mapOptions = {
        zoom: 8,
        center: classroom,
        mapTypeId: google.maps.MapTypeId.SATELLITE
    };
    var map = new google.maps.Map(
        document.getElementById("map_canvas"),
        mapOptions);
}

Simple - Hybrid

Simple - Hybrid Code

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<!DOCTYPE html>
<html>
    <head>
        <link rel="stylesheet" type="text/css" href="css/mapPage.css">
    </head>

    <body>
        <h1>Sample Map</h1>
        <div id="map_canvas"></div>

    <!-- Let's put our JavaScript down here --------------------------------------------->
        <!-- Load the external JavaScript file with the map definition code -->
        <script src="js/mapPage_03.js"></script>
        
        <!-- Load the API in asynchronous mode and execute the initialize 
            function when done -->
        <!-- The optional 'key-<API Key>' parameter is not used here but should be 
            for a production map -->
        <script async defer 
            src="https://maps.googleapis.com/maps/api/js?callback=initialize">
        </script>
    </body>
</html>

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function initialize() {
    var classroom = new google.maps.LatLng(35.084280,-106.624073)
    var mapOptions = {
        zoom: 8,
        center: classroom,
        mapTypeId: google.maps.MapTypeId.HYBRID
    };
    var map = new google.maps.Map(
        document.getElementById("map_canvas"),
        mapOptions);
}

Simple - Terrain

Simple - Terrain Code

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<!DOCTYPE html>
<html>
    <head>
        <link rel="stylesheet" type="text/css" href="css/mapPage.css">
    </head>

    <body>
        <h1>Sample Map</h1>
        <div id="map_canvas"></div>

    <!-- Let's put our JavaScript down here --------------------------------------------->
        <!-- Load the external JavaScript file with the map definition code -->
        <script src="js/mapPage_04.js"></script>
        
        <!-- Load the API in asynchronous mode and execute the initialize 
            function when done -->
        <!-- The optional 'key-<API Key>' parameter is not used here but should be 
            for a production map -->
        <script async defer 
            src="https://maps.googleapis.com/maps/api/js?callback=initialize">
        </script>
    </body>
</html>

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function initialize() {
    var classroom = new google.maps.LatLng(35.084280,-106.624073)
    var mapOptions = {
        zoom: 8,
        center: classroom,
        mapTypeId: google.maps.MapTypeId.TERRAIN
    };
    var map = new google.maps.Map(
        document.getElementById("map_canvas"),
        mapOptions);
}

Simple - Hybrid - Zoomed

Simple - Hybrid - Zoomed Code

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<!DOCTYPE html>
<html>
    <head>
        <link rel="stylesheet" type="text/css" href="css/mapPage.css">
    </head>

    <body>
        <h1>Sample Map</h1>
        <div id="map_canvas"></div>

    <!-- Let's put our JavaScript down here --------------------------------------------->
        <!-- Load the external JavaScript file with the map definition code -->
        <script src="js/mapPage_05.js"></script>
        
        <!-- Load the API in asynchronous mode and execute the initialize 
            function when done -->
        <!-- The optional 'key-<API Key>' parameter is not used here but should be 
            for a production map -->
        <script async defer 
            src="https://maps.googleapis.com/maps/api/js?callback=initialize">
        </script>
    </body>
</html>

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function initialize() {
    var classroom = new google.maps.LatLng(35.084280,-106.624073)
    var mapOptions = {
        zoom: 18,
        center: classroom,
        mapTypeId: google.maps.MapTypeId.TERRAIN
    };
    var map = new google.maps.Map(
        document.getElementById("map_canvas"),
        mapOptions);
}

Simple - Zoomed - Modified Controls

Simple - Zoomed - Modified Controls Code

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<!DOCTYPE html>
<html>
    <head>
        <link rel="stylesheet" type="text/css" href="css/mapPage.css">
    </head>

    <body>
        <h1>Sample Map</h1>
        <div id="map_canvas"></div>

    <!-- Let's put our JavaScript down here --------------------------------------------->
        <!-- Load the external JavaScript file with the map definition code -->
        <script src="js/mapPage_06.js"></script>
        
        <!-- Load the API in asynchronous mode and execute the initialize 
            function when done -->
        <!-- The optional 'key-<API Key>' parameter is not used here but should be 
            for a production map -->
        <script async defer 
            src="https://maps.googleapis.com/maps/api/js?callback=initialize">
        </script>
    </body>
</html>

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function initialize() {
var classroom = new google.maps.LatLng(35.084280,-106.624073)
var myOptions = {
    zoom: 18,
    center: classroom,
    mapTypeId: google.maps.MapTypeId.HYBRID,
    zoomControl: true,
    zoomControlOptions: {style: google.maps.ZoomControlStyle.SMALL},
    mapTypeControl: true,
    mapTypeControlOptions: {
    style: google.maps.MapTypeControlStyle.DROPDOWN_MENU},
    streetViewControl: false
};
var map = new google.maps.Map(
    document.getElementById("map_canvas"),
    myOptions);
}

Markers

Markers Code

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<!DOCTYPE html>
<html>
    <head>
        <link rel="stylesheet" type="text/css" href="css/mapPage.css">
    </head>

    <body>
        <h1>Sample Map</h1>
        <div id="map_canvas"></div>

    <!-- Let's put our JavaScript down here --------------------------------------------->
        <!-- Load the external JavaScript file with the map definition code -->
        <script src="js/mapPage_07.js"></script>
        
        <!-- Load the API in asynchronous mode and execute the initialize 
            function when done -->
        <!-- The optional 'key-<API Key>' parameter is not used here but should be 
            for a production map -->
        <script async defer 
            src="https://maps.googleapis.com/maps/api/js?callback=initialize">
        </script>
    </body>
</html>

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function initialize() {
    var classroom = new google.maps.LatLng(35.084280,-106.624073)
    var office = new google.maps.LatLng(35.084506,-106.624899)
    var myOptions = {
        zoom: 18,
        center: classroom,
        mapTypeId: google.maps.MapTypeId.HYBRID
        };
    var map = new google.maps.Map(
        document.getElementById("map_canvas"), 
        myOptions);

    var classroomMarker = new google.maps.Marker({
        position: classroom,
        title:"Geography 485L/585L Classroom, Bandelier East, Room 106"
        });
    classroomMarker.setMap(map);

    var officeMarker = new google.maps.Marker({
        position: office,
        title:"Office, Bandelier West, Room 107"
        });
    officeMarker.setMap(map);
}

Polyline

Polyline Code

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<!DOCTYPE html>
<html>
    <head>
        <link rel="stylesheet" type="text/css" href="css/mapPage.css">
    </head>

    <body>
        <h1>Sample Map</h1>
        <div id="map_canvas"></div>

    <!-- Let's put our JavaScript down here --------------------------------------------->
        <!-- Load the external JavaScript file with the map definition code -->
        <script src="js/mapPage_08.js"></script>
        
        <!-- Load the API in asynchronous mode and execute the initialize 
            function when done -->
        <!-- The optional 'key-<API Key>' parameter is not used here but should be 
            for a production map -->
        <script async defer 
            src="https://maps.googleapis.com/maps/api/js?callback=initialize">
        </script>
    </body>
</html>

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    var classroom = new google.maps.LatLng(35.084280,-106.624073)
    var office = new google.maps.LatLng(35.084506,-106.624899)
    var myOptions = {
        zoom: 18,
        center: classroom,
        mapTypeId: google.maps.MapTypeId.HYBRID
        };
    var map = new google.maps.Map(
        document.getElementById("map_canvas"), 
        myOptions);

    var classroomMarker = new google.maps.Marker({
        position: classroom,
        title:"Geography 485L/585L Classroom, Bandelier East, Room 106"
        });
    classroomMarker.setMap(map);

    var officeMarker = new google.maps.Marker({
        position: office,
        title:"Office, Bandelier West, Room 107"
        });
    officeMarker.setMap(map); 

    var officeVisitCoordinates = [
        office,
        new google.maps.LatLng(35.084445,-106.624327),
        new google.maps.LatLng(35.084309,-106.624308),
        classroom
        ];
    var officePath = new google.maps.Polyline({
        path: officeVisitCoordinates,
        strokeColor: "#FF0000",
        strokeOpacity: 1.0,
        strokeWeight: 2
    });
    officePath.setMap(map)
}

Polygon

Polygon Code

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<!DOCTYPE html>
<html>
    <head>
        <link rel="stylesheet" type="text/css" href="css/mapPage.css">
    </head>

    <body>
        <h1>Sample Map</h1>
        <div id="map_canvas"></div>

    <!-- Let's put our JavaScript down here --------------------------------------------->
        <!-- Load the external JavaScript file with the map definition code -->
        <script src="js/mapPage_09.js"></script>
        
        <!-- Load the API in asynchronous mode and execute the initialize 
            function when done -->
        <!-- The optional 'key-<API Key>' parameter is not used here but should be 
            for a production map -->
        <script async defer 
            src="https://maps.googleapis.com/maps/api/js?callback=initialize">
        </script>
    </body>
</html>

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function initialize() {
    var classroom = new google.maps.LatLng(35.084280,-106.624073)
    var office = new google.maps.LatLng(35.084506,-106.624899)
    var myOptions = {
        zoom: 18,
        center: classroom,
        mapTypeId: google.maps.MapTypeId.HYBRID
        };
    var map = new google.maps.Map(
        document.getElementById("map_canvas"), 
        myOptions);
    var classroomMarker = new google.maps.Marker({
        position: classroom,
        title:"Geography 485L/585L Classroom, Bandelier East, Room 106"
        });
    classroomMarker.setMap(map);
    var officeMarker = new google.maps.Marker({
        position: office,
        title:"Office, Bandelier West, Room 107"
        });
    officeMarker.setMap(map); 
    var buildingCoordinates = [
        new google.maps.LatLng(35.084498,-106.624921),
        new google.maps.LatLng(35.084558,-106.624911),
        new google.maps.LatLng(35.084566,-106.624970),
        new google.maps.LatLng(35.084609,-106.624966),
        new google.maps.LatLng(35.084544,-106.624383),
        new google.maps.LatLng(35.084438,-106.624317),
        new google.maps.LatLng(35.084384,-106.623922),
        new google.maps.LatLng(35.084164,-106.623970),
        new google.maps.LatLng(35.084214,-106.624324),
        new google.maps.LatLng(35.084214,-106.624324),
        new google.maps.LatLng(35.084391,-106.624284)
        ];
    var bldgPoly = new google.maps.Polygon({
        paths: buildingCoordinates,
        strokeColor: "#FF0000",
        strokeOpacity: 0.8,
        strokeWeight: 2,
        fillColor: "#FF0000",
        fillOpacity: 0.35
    });
    bldgPoly.setMap(map)
}

Adding an Info Window

Adding an Info Window Code

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<!DOCTYPE html>
<html>
    <head>
        <link rel="stylesheet" type="text/css" href="css/mapPage.css">
    </head>

    <body>
        <h1>Sample Map</h1>
        <div id="map_canvas"></div>

    <!-- Let's put our JavaScript down here --------------------------------------------->
        <!-- Load the external JavaScript file with the map definition code -->
        <script src="js/mapPage_10.js"></script>
        
        <!-- Load the API in asynchronous mode and execute the initialize 
            function when done -->
        <!-- The optional 'key-<API Key>' parameter is not used here but should be 
            for a production map -->
        <script async defer 
            src="https://maps.googleapis.com/maps/api/js?callback=initialize">
        </script>
    </body>
</html>

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function initialize() {
    var classroom = new google.maps.LatLng(35.084280,-106.624073)
    var office = new google.maps.LatLng(35.084506,-106.624899)
    var myOptions = {
        zoom: 18,
        center: classroom,
        mapTypeId: google.maps.MapTypeId.HYBRID
        };
    var map = new google.maps.Map(
        document.getElementById("map_canvas"), 
        myOptions);
    var classroomMarker = new google.maps.Marker({
        position: classroom,
        title:"Geography 485L/585L Classroom, Bandelier East, Room 106"
        });
    classroomMarker.setMap(map);
    var officeMarker = new google.maps.Marker({
        position: office,
        title:"Office, Bandelier West, Room 107"
        });
    officeMarker.setMap(map); 
    var buildingCoordinates = [
        new google.maps.LatLng(35.084498,-106.624921),
        new google.maps.LatLng(35.084558,-106.624911),
        new google.maps.LatLng(35.084566,-106.624970),
        new google.maps.LatLng(35.084609,-106.624966),
        new google.maps.LatLng(35.084544,-106.624383),
        new google.maps.LatLng(35.084438,-106.624317),
        new google.maps.LatLng(35.084384,-106.623922),
        new google.maps.LatLng(35.084164,-106.623970),
        new google.maps.LatLng(35.084214,-106.624324),
        new google.maps.LatLng(35.084214,-106.624324),
        new google.maps.LatLng(35.084391,-106.624284)
        ];
    var bldgPoly = new google.maps.Polygon({
        paths: buildingCoordinates,
        strokeColor: "#FF0000",
        strokeOpacity: 0.8,
        strokeWeight: 2,
        fillColor: "#FF0000",
        fillOpacity: 0.35
        });
    bldgPoly.setMap(map);
    var classInfoContent = '<div class="infoBox">' +
        '<p>This is the location for the Geography 485L/585L class</p>' +
        '</div>'
    var classInfoWindow = new google.maps.InfoWindow({
        content: classInfoContent
        });
    google.maps.event.addListener(classroomMarker, 'click', function() {
        classInfoWindow.open(map,classroomMarker);
        });
}

Overview

• Geographic Information Systems
  • Data Types
  • Coordinate Systems
• Services Oriented Architectures
  • Historic Context
  • Current Model - Network Computing
  • Components
  • Interoperability Standards

Data Types - Vector

• Vector data represent phenomena that are associated with specific bounded locations, typically represented by:
  • Points
  • Lines
  • Polygons
• Vector data include:
  • The geometries that describe the area being referenced, and
  • Attributes associated with that area

For example, a census vector data product might include the geometries that define census tracts and attributes associated with each geometry: population, income, etc.

Data Types - Raster

• Raster data are frequently used to represent values for phenomena that vary continuously across space (e.g. elevation, concentration of air pollutants, depth to ground water, etc. )

• These values are encoded over a regular grid of observation locations with a specified grid spacing - often referred to as the spatial resolution of the dataset (i.e. 10m resolution for a standard USGS Digital Elevation Model product)

• Often parts of data collections that are repeated (i.e. remote sensing data products)

Accessing and Processing Raster and Vector Data - Programmatically

• Two geospatial libraries and their related utility programs provide information about and tools for modifying vector and raster data sets

OGR

vector data access and information

GDAL

raster data access and information

These libraries are the data access and processing foundation for a growing number of open source and commercial mapping systems

Information and documentation: GDAL Home Page | OGR Home Page

Coordinate Systems/Projections

• To convert locations from a 3-dimensional oblate spherical coordinate system (such as is commonly used to represent the surface of the earth) to a 2-dimensional representation in a map, a coordinate transformation must be performed.
• There are a limitless number of potential coordinate transformations possible, and a large number have been named and defined that meet specific cartographic or other requirements

EPSG Codes

• A catalog of numeric codes and associated coordinate transformation parameters is maintained by the International Association of Oil & Gas Producers (OGP) - the successor scientific organization to the European Petroleum Survey Group (EPSG)

• These numeric codes are used by many desktop and online mapping systems to document and represent the coordinate systems of available data and services

• Links to an online version of the registry and downloadable databases of the registry are available from: http://www.epsg.org/Geodetic.html.

Projection Parameters

The parameters that define a map projection may be looked up in a number of online locations:

EPSG registry

Helpful if you already know the EPSG code of the projection you are looking for - http://www.epsg-registry.org/

GeoTIFF Projection List

Helpful if you know the name of one of the broadly used projections - uneven performance of links - http://www.remotesensing.org/geotiff/proj_list/

SpatialReference.org

Decent search tool, includes non-EPSG as well as EPSG projection information, multiple descriptions of projection parameters - http://spatialreference.org/

Network Computing Timeline

• Predecessor to the Internet - ARPANET (1969). Interconnection between UCLA and SRI (Menlo Park)
• Adoption of TCP/IP as next generation protocol for ARPANET (1983)
• NSF commissions construction of NSFNET, also based upon TCP/IP (1983)
• NSFNET opened to commercial connections (1988). Led to interconnection of multiple, previously separate networks into an “Internet”
• Growth of internet users has expanded rapidly over the past decade

In a Phrase ...

The current networking computing model consists of Components Interacting with Each Other

So - We Need to Answer the Following Questions

What are components?

What does it mean to interact?

Key Components - Data

Database systems

• Optimized for storing massive quantities of tabular data
• May be spatially enabled to support the storage of geometries (points, lines, polygons) in addition to related attribute data
• Standard language (Structured Query Language [SQL]) for interacting with many databases
• Broad support for accessing the contents of databases from many other applications and programming languages, for example:
  • Spreadsheets
  • Statistical Software
  • Geographic Information Systems (GIS)

Key Components - Data

File-based data

• Often stored on the file system
• Sometimes difficult represent data within a database structure (i.e. binary data)
• May be in a wide variety of formats
  • XML
  • ASCII Text (e.g. CSV, tab-delimited)
  • Binary files
  • Excel Spreadsheets
  • Word Processing Documents
  • Geospatial data (e.g. imagery)
• Remotely Accessible Data
  • Some data may be provided through reference to an external network resource (i.e. a web address, or other identifier) or service

Key Components - Processing Services

• Perform modification of source data to generate a new data product

• May be “chained” together to create a processing “workflow”. Output from one processing service may be used as the input to another

• May be simple OGC services; or complex data processing, analysis, or visualization services. Examples include
  • Extraction of a subset of a large data set based upon provided search criteria
  • Generation of a map from a collection of data
  • Fusion of two data products into a single derived product (e.g. vegetation indices calculated from multiple remote sensing images)
  • Calculation of statistical information for an input product, and delivery of the statistical summary

Key Components - Clients

• Any system that accesses the services provided by the system may be considered a “client”
• That system may be manually operated by a human user, or triggered automatically by software
• Human operated clients include
  • Web-based applications
  • Desktop applications such as Geographic Information Systems and Statistical Analysis tools
• Machine clients include
  • Data processing services that translate requests to them into requests for other system services
  • Regularly scheduled requests that are automatically triggered by external computer systems.

Open Geospatial Consortium (OGC) Standards

• Two Classes of Standards Considered Here
  • Geospatial Product Access Standards
  • Geospatial Data and Representation Standards
• Product Access Standards
  • Web Map Services (WMS)
  • Web Feature Services (WFS)
  • Web Coverage Services (WCS)
• Data and Representation Standards
  • Geography Markup Language (GML)
  • KML (formerly known as Keyhole Markup Language)

OGC Web Feature Services (WMS) Characteristics

• HTTP GET (required), HTTP POST (optional)
• Requests:
  • GetCapabilities
  • GetMap
  • GetFeatureInfo
• Returns
  • Mapped data
  • XML Capabilities Document, Feature Attributes
• Includes support for time-based requests

OGC Web Feature Services (WFS) Characteristics

• Either HTTP GET or POST required
• Requests
  • GetCapabilities
  • DescribeFeatureType
  • GetFeature/GetFeatureWithLock
  • GetGmlObject
  • LockFeature
  • Transaction
• Returns
  • XML (GML)
  • Capabilities
  • Feature Data

OGC Web Coverage Services (WCS) Characteristics

• Either HTTP GET or POST required
• Requests
  • GetCapabilities
  • DescribeCoverage
  • GetCoverage
• Returns
  • Geospatial data for coverage
  • XML Capabilities
• Includes support for time-based requests

OGC Geography Markup Language (GML)

• GML is an XML grammar for representing geospatial features and their associated attributes
• In its generic form it can encode points, lines, and polygons and their associated attributes
• As an XML schema GML was designed to be extensible by communities of practice for consistent encoding of geographic data more richly than allowed by the generic default model
• GML documents representing large complex geometries can be quite large - therefore slow to transfer over the Internet

OGC KML

• An XML specification that supports the encoding of representation and embedding of geospatial data for use in geospatial viewers
• Began as the underlying representation language of Google Earth (originally developed by Keyhole for their virtual Earth viewer)
• Adopted as an OGC standard in 2008
• Supports data linkage through
  • Embedding
  • Reference through external URLs - with WMS specifically supported through parameterization
• Includes support for the representation of time in relation to data objects

OGC Summary

The OGC web service specifications support key geospatial data access requirements

WMS

visualization of geospatial data through simple web requests

WFS

delivery of geospatial data (typically points, lines, and polygons) in a format that is usable in GIS and other applications

WCS

delivery of geospatial data (typically, but not limited to, raster data) usable in other applications

OGC Summary

The OGC data and representation standards support data exchange and higher level representation

GML

XML schema for the representation of features and associated attributes. It may be extended for use by specific communities of users (i.e. ecological data models)

KML

XML schema that supports the combination of embedded data and external data into a complete representation model that may be used by client applications to present the data through a user interface (e.g. Google Earth, WorldWind)

Overview

• Extensible Markup Language - XML
  • Definition of a markup language
  • Requirements
  • Extensible ???
• KML - AKA Keyhole Markup Language
  • An XML Document Format
  • Combined representation of spatial data and time
• OGC Web Map Services (WMS)
  • Requests and Results
  • GetCapabilities, GetMap, GetFeatureInfo
• Integration of WMS into KML

XML Design Goals

• XML shall be straightforwardly usable over the Internet.
• XML shall support a wide variety of applications.
• XML shall be compatible with SGML.
• It shall be easy to write programs which process XML documents.
• The number of optional features in XML is to be kept to the absolute minimum, ideally zero.
• XML documents should be human-legible and reasonably clear.
• The XML design should be prepared quickly.
• The design of XML shall be formal and concise.
• XML documents shall be easy to create.
• Terseness in XML markup is of minimal importance.

From XML 1.0 (5th ed.) Recommendation

XML Structure - Well Formed / Valid

• Well Formed XML - a document that conforms to the structural definition of XML. Either well-formed, or not XML
• Valid XML - a document that is both well-formed and conforms to a specific content structure defined by
  • A Document Type Definition (DTD) - the original XML specification for the definition of the content of a specific XML document
  • A Schema document - defined in a variety of languages (e.g. W3C Schema, RELAX NG, Schematron, ISO DSDL, etc.)

XML Wikipedia Article

Simple XML Document

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<?xml version="1.0" encoding="ISO-8859-1"?>
<!-- Some comment would go here to describe this document ... -->
<note>
    <to>Tove</to>
    <from>Jani</from>
    <heading>Reminder</heading>
    <body type="instruction" >Don't forget me this weekend!</body>
</note>

XML Prolog

Includes XML Declaration and Comment

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<?xml version="1.0" encoding="ISO-8859-1"?>
<!-- Some comment would go here to describe this document ... -->

XML Elements

Define blocks of content

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<note>
    <to>Tove</to>
    <from>Jani</from>
    <heading>Reminder</heading>
    <body type="instruction" >Don't forget me this weekend!</body>
</note>

XML Root Element

• Required
• There is only one
• It must be a pair of opening and closing tags

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<note>
    ...
    ...
    ...
    ...
</note>

XML Content Elements

• Contain all other document content
• May be paired opening and closing tags, or
• May be self-closing with a terminal "/" in the element, e.g. <br />

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    <to>Tove</to>
    <from>Jani</from>
    <heading>Reminder</heading>
    <body type="instruction" >Don't forget me this weekend!</body>

XML Attributes

Define additional information about elements as name=value pairs.

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    <body type="instruction" >Don't forget me this weekend!</body>

XML Element Content

The material contained between the opening and closing tags of an Element.

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    <body type="instruction" >Don't forget me this weekend!</body>

Valid XML?

Why is this XML well-formed but not valid?

There is no DTD or Schema defined for the document against which it can be validated

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<?xml version="1.0" encoding="ISO-8859-1"?>
<!-- Edited by XMLSpy® -->
<note>
    <to>Tove</to>
    <from>Jani</from>
    <heading>Reminder</heading>
    <body type="instruction" >Don't forget me this weekend!</body>
</note>

Common XML Constructs

Document Type Declaration (DTD) references (PROLOG)

definition, either by reference or by direct inclusion, the allowed structure of an XML document, for example:


<!DOCTYPE greeting SYSTEM "hello.dtd">

CDATA Sections

blocks of XML that contain characters that would otherwise be recognized as XML markup, for example:


<![CDATA[<greeting>Hello, world!</greeting>]]>

XML Namespace Declarations

additional information included in elements to distinguish between duplicate element names, for example (declared in lines 1-3, used in lines 5-17):


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<root 
    xmlns:h="http://www.w3.org/TR/html4/" 
    xmlns:f="http://www.w3schools.com/furniture">

<h:table>
    <h:tr>
        <h:td>Apples</h:td>
        <h:td>Bananas</h:td>
    </h:tr>
</h:table>
<f:table>
    <f:legs>4</f:legs>
    <f:cost>300</f:cost>
    <f:width>3</f:width>
    <f:length>5</f:length>
    <f:height>4</f:height>
</f:table>
</root>

KML Background

• An XML grammar originally developed as Keyhole Markup Language by Keyhole, Inc. for use in their Keyhole Earth Viewer.
• Google acquired Keyhole, Inc. in 2004
• KML version 2.2 became an OGC standard in 2008
• Two delivered KML file formats

KML

an XML document, with a “.kml” extension that is directly readable and editable

KMZ

a compressed (zipped) file with a “.kmz” extension¹, that contains at least a KML document, but may contain other files as well.

KML Capabilities

• Annotate the Earth
• Specify icons and labels to identify locations on the surface of the planet
• Create different camera positions to define unique views for KML features
• Define image overlays to attach to the ground or screen
• Define styles to specify KML feature appearance
• Write HTML descriptions of KML features, including hyperlinks and embedded images
• Organize KML features into hierarchies using folder elements
• Locate and update retrieved KML documents from local or remote network locations
• Define the location and orientation of textured 3D objects

KML Content

• Model for encoding 2- and 3-dimensional geometries for use in 2-D mappers and 3-D virtual globe applications
• Uses latitude-longitude (based upon WGS84 datum) for encoding horizontal position
• Represents altitude in Meters (based upon the WGS84 ellipsoid and EGM96 geoid)

High-Level KML Content Types

Features

including documents, folders, placemarks, network links

Geometries

including points, linestrings, polygons, models, locations

Overlays

including ground overlays, lat-lon boxes, photo overlays, screen overlays

Styles

styles, substyles, icons, label styles

Links

read, update, create, delete, change

Views

camera, look at

Time

time span, timestamp

KML Demonstration and References

New Mexico State Boundary KML File | KMZ File (from NM RGIS)

Google Code KML Documentation

OGC KML Implementation specification

WMS GetCapabilities

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http://gstore.unm.edu/apps/rgis/datasets/6ca5428a-a78c-4c82-8120-
da70dc92f2cc/services/ogc/wms?
    SERVICE=wms&
    REQUEST=GetCapabilities&
    VERSION=1.1.1

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<?xml version='1.0' encoding="ISO-8859-1" standalone="no" ?>
<!DOCTYPE WMT_MS_Capabilities SYSTEM "http://schemas.opengis.net/wms/1.1.1/
WMS_MS_Capabilities.dtd"
 [
 <!ELEMENT VendorSpecificCapabilities EMPTY>
 ]>  <!-- end of DOCTYPE declaration -->

<WMT_MS_Capabilities version="1.1.1">

<!-- MapServer version 6.0.3 OUTPUT=GIF OUTPUT=PNG OUTPUT=JPEG OUTPUT=KML SUPPORTS=PROJ 
SUPPORTS=AGG SUPPORTS=FREETYPE SUPPORTS=ICONV SUPPORTS=WMS_SERVER SUPPORTS=WMS_CLIENT 
SUPPORTS=WFS_SERVER SUPPORTS=WFS_CLIENT SUPPORTS=WCS_SERVER SUPPORTS=SOS_SERVER 
INPUT=POSTGIS INPUT=OGR INPUT=GDAL INPUT=SHAPEFILE -->

<Service>
  <Name>OGC:WMS</Name>
  <Title>tl_2010_35_state10</Title>
  <Abstract>WMS Service for RGIS dataset State Boundary - 2010 
  (6ca5428a-a78c-4c82-8120-da70dc92f2cc)</Abstract>
        <KeywordList>
          <Keyword>RGIS</Keyword>
          <Keyword> New Mexico</Keyword>
        </KeywordList>
  <OnlineResource xmlns:xlink="http://www.w3.org/1999/xlink" 
  xlink:href="http://gstore.unm.edu/apps/rgis/datasets/6ca5428a-a78c-4c82-8120-
  da70dc92f2cc/services/ogc/wms"/>
  <ContactInformation>
    <ContactPersonPrimary>
      <ContactPerson>GStore Support</ContactPerson>
      <ContactOrganization>Earth Data Analysis Center</ContactOrganization>
    </ContactPersonPrimary>
      <ContactPosition>technical support</ContactPosition>
    <ContactAddress>
        <AddressType>Mailing address</AddressType>
        <Address>Earth Data Analysis Center, MSC01 1110, 
        1 University of New Mexico</Address>
        <City>Albuquerque</City>
        <StateOrProvince>NM</StateOrProvince>
        <PostCode>87131</PostCode>
        <Country>US</Country>
    </ContactAddress>
      <ContactVoiceTelephone>(505) 277-3622</ContactVoiceTelephone>
      <ContactFacsimileTelephone>(505) 277-3614</ContactFacsimileTelephone>
  <ContactElectronicMailAddress>gstore@edac.unm.edu</ContactElectronicMailAddress>
  </ContactInformation>
  <Fees>None</Fees>
  <AccessConstraints>none</AccessConstraints>
</Service>

<Capability>
  <Request>
    <GetCapabilities>
      <Format>application/vnd.ogc.wms_xml</Format>
      <DCPType>
        <HTTP>
          <Get><OnlineResource xmlns:xlink="http://www.w3.org/1999/xlink" 
          xlink:href="http://gstore.unm.edu/apps/rgis/datasets/6ca5428a-a78c-4c82-
          8120-da70dc92f2cc/services/ogc/wms?"/></Get>
          <Post><OnlineResource xmlns:xlink="http://www.w3.org/1999/xlink" 
          xlink:href="http://gstore.unm.edu/apps/rgis/datasets/6ca5428a-a78c-4c82-
          8120-da70dc92f2cc/services/ogc/wms?"/></Post>
        </HTTP>
      </DCPType>
    </GetCapabilities>
    <GetMap>
      <Format>image/png</Format>
      <Format>image/gif</Format>
      <Format>image/jpeg</Format>
      <Format>image/png; mode=8bit</Format>
      <Format>image/tiff</Format>
      <Format>application/vnd.google-earth.kml+xml</Format>
      <Format>application/vnd.google-earth.kmz</Format>
      <DCPType>
        <HTTP>
          <Get><OnlineResource xmlns:xlink="http://www.w3.org/1999/xlink" 
          xlink:href="http://gstore.unm.edu/apps/rgis/datasets/6ca5428a-a78c-4c82-
          8120-da70dc92f2cc/services/ogc/wms?"/></Get>
          <Post><OnlineResource xmlns:xlink="http://www.w3.org/1999/xlink" 
          xlink:href="http://gstore.unm.edu/apps/rgis/datasets/6ca5428a-a78c-4c82-
          8120-da70dc92f2cc/services/ogc/wms?"/></Post>
        </HTTP>
      </DCPType>
    </GetMap>
    <GetFeatureInfo>
      <Format>text/plain</Format>
      <Format>application/vnd.ogc.gml</Format>
      <DCPType>
        <HTTP>
          <Get><OnlineResource xmlns:xlink="http://www.w3.org/1999/xlink" 
          xlink:href="http://gstore.unm.edu/apps/rgis/datasets/6ca5428a-a78c-4c82-
          8120-da70dc92f2cc/services/ogc/wms?"/></Get>
          <Post><OnlineResource xmlns:xlink="http://www.w3.org/1999/xlink" 
          xlink:href="http://gstore.unm.edu/apps/rgis/datasets/6ca5428a-a78c-4c82-
          8120-da70dc92f2cc/services/ogc/wms?"/></Post>
        </HTTP>
      </DCPType>
    </GetFeatureInfo>
    <DescribeLayer>
      <Format>text/xml</Format>
      <DCPType>
        <HTTP>
          <Get><OnlineResource xmlns:xlink="http://www.w3.org/1999/xlink" 
          xlink:href="http://gstore.unm.edu/apps/rgis/datasets/6ca5428a-a78c-4c82-8120-
          da70dc92f2cc/services/ogc/wms?"/></Get>
          <Post><OnlineResource xmlns:xlink="http://www.w3.org/1999/xlink" 
          xlink:href="http://gstore.unm.edu/apps/rgis/datasets/6ca5428a-a78c-4c82-8120-
          da70dc92f2cc/services/ogc/wms?"/></Post>
        </HTTP>
      </DCPType>
    </DescribeLayer>
    <GetLegendGraphic>
      <Format>image/png</Format>
      <Format>image/gif</Format>
      <Format>image/jpeg</Format>
      <Format>image/png; mode=8bit</Format>
      <DCPType>
        <HTTP>
          <Get><OnlineResource xmlns:xlink="http://www.w3.org/1999/xlink" 
          xlink:href="http://gstore.unm.edu/apps/rgis/datasets/6ca5428a-a78c-4c82-8120-
          da70dc92f2cc/services/ogc/wms?"/></Get>
          <Post><OnlineResource xmlns:xlink="http://www.w3.org/1999/xlink" 
          xlink:href="http://gstore.unm.edu/apps/rgis/datasets/6ca5428a-a78c-4c82-8120-
          da70dc92f2cc/services/ogc/wms?"/></Post>
        </HTTP>
      </DCPType>
    </GetLegendGraphic>
    <GetStyles>
      <Format>text/xml</Format>
      <DCPType>
        <HTTP>
          <Get><OnlineResource xmlns:xlink="http://www.w3.org/1999/xlink" 
          xlink:href="http://gstore.unm.edu/apps/rgis/datasets/6ca5428a-a78c-4c82-8120-
          da70dc92f2cc/services/ogc/wms?"/></Get>
          <Post><OnlineResource xmlns:xlink="http://www.w3.org/1999/xlink" 
          xlink:href="http://gstore.unm.edu/apps/rgis/datasets/6ca5428a-a78c-4c82-8120-
          da70dc92f2cc/services/ogc/wms?"/></Post>
        </HTTP>
      </DCPType>
    </GetStyles>
  </Request>
  <Exception>
    <Format>application/vnd.ogc.se_xml</Format>
    <Format>application/vnd.ogc.se_inimage</Format>
    <Format>application/vnd.ogc.se_blank</Format>
  </Exception>
  <VendorSpecificCapabilities />
  <UserDefinedSymbolization SupportSLD="1" UserLayer="0" UserStyle="1" RemoteWFS="0"/>
  <Layer>
    <Name>tl_2010_35_state10</Name>
    <Title>tl_2010_35_state10</Title>
    <Abstract>WMS Service for RGIS dataset State Boundary - 2010 
    (6ca5428a-a78c-4c82-8120-da70dc92f2cc)</Abstract>
    <KeywordList>
     <Keyword>RGIS</Keyword>
     <Keyword> New Mexico</Keyword>
    </KeywordList>
    <SRS>EPSG:4269</SRS>
    <SRS>EPSG:4326</SRS>
    <SRS>EPSG:4267</SRS>
    <SRS>EPSG:26913</SRS>
    <SRS>EPSG:26912</SRS>
    <SRS>EPSG:26914</SRS>
    <SRS>EPSG:26713</SRS>
    <SRS>EPSG:26712</SRS>
    <SRS>EPSG:26714</SRS>
    <SRS>EPSG:3857</SRS>
    <LatLonBoundingBox minx="-109.05" miny="31.3322" maxx="-103.002" maxy="37.0003" />
    <BoundingBox SRS="EPSG:4326"
                minx="-109.05" miny="31.3322" maxx="-103.002" maxy="37.0003" />
    <Layer queryable="1" opaque="0" cascaded="0">
        <Name>tl_2010_35_state10</Name>
        <Title>tl_2010_35_state10</Title>
        <Abstract>State Boundary - 2010</Abstract>
        <KeywordList>
          <Keyword></Keyword>
        </KeywordList>
        <SRS>epsg:4326</SRS>
        <LatLonBoundingBox minx="-109.05" miny="31.3322" maxx="-103.002" maxy="37.0003" />
        <BoundingBox SRS="epsg:4326"
                    minx="-109.05" miny="31.3322" maxx="-103.002" maxy="37.0003" />
        <MetadataURL type="FGDC-STD-001-1998">
          <Format>text/xml</Format>
          <OnlineResource xmlns:xlink="http://www.w3.org/1999/xlink" xlink:type="simple" 
          xlink:href="http://gstore.unm.edu/apps/rgis/datasets/6ca5428a-a78c-4c82-8120-da70dc92f2cc/metadata/FGDC-STD-001-1998.xml"/>
        </MetadataURL>
        <Style>
          <Name>default</Name>
          <Title>default</Title>
          <LegendURL width="72" height="22">
             <Format>image/png</Format>
             <OnlineResource xmlns:xlink="http://www.w3.org/1999/xlink" xlink:type="simple" 
             xlink:href="http://gstore.unm.edu/apps/rgis/datasets/6ca5428a-a78c-4c82-8120-da70dc92f2cc/services/ogc/wms?version=1.1.1&amp;service=WMS&amp;request=GetLegendGraphic&amp;layer=tl_2010_35_state10&amp;format=image/png&amp;STYLE=default"/>
          </LegendURL>
        </Style>
    </Layer>
  </Layer>
</Capability>
</WMT_MS_Capabilities>

WMS GetMap

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http://gstore.unm.edu/apps/rgis/datasets/ 6ca5428a-a78c-4c82-8120-da70dc92f2cc/ services/ogc/wms? VERSION=1.1.1& SERVICE=WMS& REQUEST=GetMap& BBOX=-109,31,-102.9,37.1& LAYERS=tl_2010_35_state10& WIDTH=200& HEIGHT=200& SRS=EPSG:4326& FORMAT=image/jpeg& STYLES=

link

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http://gstore.unm.edu/apps/rgis/datasets/ 6ca5428a-a78c-4c82-8120-da70dc92f2cc/ services/ogc/wms? VERSION=1.1.1& SERVICE=WMS& REQUEST=GetMap& BBOX=-109,31,-102.9,37.1& LAYERS=tl_2010_35_state10& WIDTH=300& HEIGHT=300& SRS=EPSG:4326& TRANSPARENT=TRUE& FORMAT=image/png& STYLES=

link

Integraton of WMS and KML

• The KML GroundOverlay element may be used to integrate a network accessible map image into a client
• A WMS service may be used to as the source of a KML GroundOverlay element
• KML includes parameterizations that allow for dynamic generation of WMS requests using client bounding box information
• Time-enabled WMS may be accessed through use of manually configured time parameters in WMS URLs and TimeStamp or TimeSpan KML elements

Sample WMS-KML Integration

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<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://www.opengis.net/kml/2.2" xmlns:gx="http://www.google.com/kml/ext/2.2" 
    xmlns:kml="http://www.opengis.net/kml/2.2" xmlns:atom="http://www.w3.org/2005/Atom">
    <GroundOverlay>
        <name>RGIS Counties WMS</name>
        <Icon>
            <href>http://gstore.unm.edu/apps/rgis/datasets/107046/services/ogc/wms?
            VERSION=1.1.1&amp;SERVICE=WMS&amp;REQUEST=GetMap&amp;BBOX=-109,31,-102.9,37.1
            &amp;LAYERS=tl_2010_35_state10&amp;WIDTH=800&amp;HEIGHT=800&amp;SRS=EPSG:4326
            &amp;FORMAT=image/png&amp;STYLES=</href>
            <viewRefreshMode>onStop</viewRefreshMode>
        </Icon>
        <LatLonBox>
            <north>37.32753828398865</north>
            <south>30.86418272137246</south>
            <east>-101.3630220689848</east>
            <west>-110.6891149310152</west>
        </LatLonBox>
    </GroundOverlay>
</kml>

Overview

• OGC Web Feature Services (WFS)
  • Capabilities and purpose
  • Overview of the collection of WFS commands
  • Sample WFS requests
• OGC Web Coverage Services (WCS)
  • Capabilities and purpose
  • Overview of the collection of WCS commands
  • Sample WCS requests

Background

The documents related to the OGC WFS standard are available from: http://www.opengeospatial.org/standards/wfs and all operation parameter tables presented here are based upon the OpenGIS Web Feature Service 2.0 Interface Standard - Panagiotis (Peter) A. Vretanos, editor - 2010-11-02

From the Version 2.0.0 WFS Scope Section:

This International Standard specifies the behaviour of a service that provides transactions on and access to geographic features in a manner independent of the underlying data store. It specifies discovery operations, query operations, locking operations, transaction operations and operations to manage stored parameterized query expressions.

Discovery operations allow the service to be interrogated to determine its capabilities and to retrieve the application schema that defines the feature types that the service offers.

Query operations allow features or values of feature properties to be retrieved from the underlying data store based upon constraints, defined by the client, on feature properties.

Locking operations allow exclusive access to features for the purpose of modifying or deleting features.

Transaction operations allow features to be created, changed, replaced and deleted from the underlying data store.

Stored query operations allow clients to create, drop, list and described parameterized query expressions that are stored by the server and can be repeatedly invoked using different parameter values.

WFS Requests/Operations

These request types are submitted as part of the required REQUEST key in a KVP HTTP GET request.

GetCapabilities

service metadata (XML) that documents the types of features supported by the service and the operations supported by each feature type

DescribeFeatureType

metadata (XML) that describes the structure of supported feature types

GetPropertyValue

a request for the value(s) of a specified property for a specified featuretype

GetFeature (GetFeatureWithLock)

a request for actual features (XML, or other formats) from the service. The request may include both spatial and non-spatial query constraints

LockFeature

Feature locking operation

Transaction

a request to a WFS that may create, update, or delete features

CreateStoredQuery

a request to create a named WFS query that is stored on the server for future reuse

DropStoredQuery

a request to remove a named WFS query that has previously been stored on the server

ListStoredQueries

a request to retrieve a list of named WFS queries that have been stored on the server

DescribeStoredQueries

a request for more detailed information about specific named WFS queries that are stored on the server

WFS Conformance Levels

WFS 2.0.0 Requests and their corresponding WFS Compliance Levels

Operation (REQUEST=)	V 1.1.0	V 2.0.0	Simple	Basic	Transactional	Locking
GetCapabilities
DescribeFeatureType
ListStoredQueries
DescribeStoredQueries
GetFeature
StoredQuery
GetPropertyValue
Transaction
GetFeatureWithLock
LockFeature
GetGMLObject

Request Composition

Requests submitted to a WFS may be submitted either via

HTTP GET

a request that includes all request parameters within the URL submitted to the service. Request parameters are included in the URL as “key=value” pairs (KVPs)

HTTP POST

a request where the URL consists of only the Host and path, with all other request parameters included in the body of the POST document submitted to the service. The request parameters supplied to the server are encoded as XML within the POST document.

SOAP

a request submitted as an encapsulated message within a SOAP transaction.

Servers implementing WFS may support either the HTTP GET, POST, or SOAP request model

Conceptually FeatureType = Layer

KVP for Base WFS Requests

Base request parameters for all HTTP GET KVP requests (Figure 1)

VERSION is required for all operations except the GetCapabilities request

Sample GetCapabilities Requests

Sample request to USGS Framework Layer (Governmental Units) WFS Service advertised by the USGS TNM Access API page service list - Live Link

http://services.nationalmap.gov/arcgis/services/WFS/govunits/MapServer/WFSServer?
    request=GetCapabilities&
    service=WFS

Sample request to NM RGIS (NM 2010 Census Block Groups) - Live Link

http://gstore.unm.edu/apps/rgis/datasets/715663ba-c1c3-414c-84a7-c671526f8316/services/ogc/wfs?
    SERVICE=wfs&
    REQUEST=GetCapabilities&
    VERSION=1.0.0

KVP for DescribeFeatureType Request

DescribeFeatureType HTTP GET KVP request (Figure 2)

Sample DescribeFeatureType Requests

USGS Framework Layer (Governmental Units) WFS Service linked from the USGS TNM Access API page service list - Live Link

http://services.nationalmap.gov/arcgis/services/WFS/govunits/MapServer/WFSServer?
    version=1.1.0&
    request=DescribeFeatureType&
    service=WFS&
    typeName=WFS_govunits:State_or_Territory_High-res

Sample request to NM RGIS (NM 2010 Census Block Groups) - Live Link

http://gstore.unm.edu/apps/rgis/datasets/715663ba-c1c3-414c-84a7-c671526f8316/services/ogc/wfs?
    VERSION=1.0.0&
    SERVICE=wfs&
    REQUEST=DescribeFeatureType&
    TYPENAME=tl_2010_35_bg10

KVP for GetFeature Request

GetFeature HTTP GET KVP request (Figure 3)

KVP for GetFeature Request - Presentation Parameters (Figure {4})

KVP for GetFeature Request - Resolve Parameters (Figure {5})

KVP for GetFeature Request - Ad-hoc Query Parameters (Figure {6})

KVP for GetFeature Request - Stored Query Parameters (Figure {6})

Sample GetFeature Requests

USGS Framework Layer (Governmental Units) WFS Service linked from the USGS TNM Access API page service list - Live Link

Note: TYPENAME for VERSION=1.1.0 instead of TYPENAMES for VERSION=2.0.0

http://services.nationalmap.gov/arcgis/services/WFS/govunits/MapServer/WFSServer?
    VERSION=1.1.0&
    REQUEST=GetFeature&
    SERVICE=WFS&
    TYPENAME=WFS_govunits:State_or_Territory_High-res

Alternative request (Live Link) that includes an OUTPUTFORMAT parameter

http://services.nationalmap.gov/arcgis/services/WFS/govunits/MapServer/WFSServer?
    VERSION=1.1.0&
    REQUEST=GetFeature&
    SERVICE=WFS&
    TYPENAME=WFS_govunits:State_or_Territory_High-res&
    OUTPUTFORMAT=text/xml;%20subType=gml/3.1.1/profiles/gmlsf/1.0.0/0

Background

The documents related to the OGC WCS standard are available from: [http://www.opengeospatial.org/standards/wcs][wcs] with the sample parameters in the following slides based upon the OGC Web Coverage Service 2.0 Interface Standard - KVP Protocol Binding Extension - Peter Baumann, editor - 2010-10-27

From the OGC WCS 2.0 Introduction

The OGC Web Coverage Service (WCS) supports electronic retrieval of geospatial data as "coverages" – that is, digital geospatial information representing space/time-varying phenomena.

This document specifies the WCS core; every implementation of a WCS shall adhere to this standard. This standard thus defines only basic requirements. Extensions to the core will define extensions to meet additional requirements, such as the response encoding. Indeed, additional extensions are required in order to completely specify a WCS for implementation.

A WCS provides access to coverage data in forms that are useful for client-side rendering, as input into scientific models, and for other clients. The WCS may be compared to the OGC Web Feature Service (WFS) and the Web Map Service (WMS). As WMS and WFS service instances, a WCS allows clients to choose portions of a server's information holdings based on spatial constraints and other query criteria.

WCS Requests/Operations

GetCapabilities

service metadata (XML) that documents the service, including brief information about the data coverages available from the service

DescribeCoverage

a request for more detailed metadata (XML) for one or more coverages listed in the output of the GetCapabilities request

GetCoverage

a request for an actual data product representing a specified coverage. The specific data formats available for delivery will vary from service to service.

Request Composition

Requests submitted to a WCS may be submitted either via the following protocols, as defined in the three extensions developed thus far for the core WCS standard.

HTTP GET

a request that includes all request parameters within the URL submitted to the service. Request parameters are included in the URL as “name=value” pairs. Extension Link

HTTP POST

a request where the URL consists of only the Host and path, with all other request parameters included in the body of the POST document submitted to the service. The request parameters supplied to the server are encoded as XML within the POST document. Extension Link

XML/SOAP

a request-response model between the client that conforms with the W3C SOAP web services protocol Extension Link

KVP for Base WCS Requests

Sample WCS GetCapabilities requests

NOAA Global Forecast System THREDDS catalog. Live Link

http://nomads.ncdc.noaa.gov/thredds/wcs/gfs-004/201602/20160228/
    gfs_4_20160228_0000_384.grb2?
    service=WCS&
    version=1.0.0&
    request=GetCapabilities 

New Mexico Resource Geographic Information System PRISM Precipitation Normals WCS Service. Live Link

http://gstore.unm.edu/apps/rgis/datasets/2ce10b57-3925-4971-b876-b6fc66d3cca2/services/ogc/wcs?
    SERVICE=wcs&
    REQUEST=GetCapabilities&
    VERSION=1.1.2

KVP for DescribeCoverage Request

DescribeCoverage HTTP GET KVP request (Figure 8)

Sample DescribeCoverage Request

NOAA Global Forecast System THREDDS catalog. Live Link

http://nomads.ncdc.noaa.gov/thredds/wcs/gfs-004/201602/20160228/
gfs_4_20160228_0000_384.grb2?
    service=WCS&
    version=1.0.0&
    request=DescribeCoverage&
    COVERAGE=Categorical_Rain 

New Mexico Resource Geographic Information System PRISM Precipitation Normals WCS Service. Live Link

http://gstore.unm.edu/apps/rgis/datasets/2ce10b57-3925-4971-b876-b6fc66d3cca2/services/ogc/wcs?
    SERVICE=wcs&
    REQUEST=DescribeCoverage&
    VERSION=1.1.2&
    COVERAGE=us_ppt_1971_2000_11

KVP for GetCoverage Request

GetCoverage HTTP GET KVP request (Figure 8)

Subset Definition for GetCoverage Request

Subset definition for the GetCoverage HTTP GET KVP request (Figure 10)

Example from the 2.0 specification:

http://www.myserver.org:port/path?
    service=WCS
    &version=2.0
    &request=GetCoverage
    &coverageId=C0002
    &subset=lon,http://www.opengis.net/def/crs/EPSG/0/4326(-71,47)
    &subset=lat,http://www.opengis.net/def/crs/EPSG/0/4326(-66,51)
    &subset=t,http://www.opengis.net/def/trs/ISO- 8601/0/Gregorian+UTC("2009-11-06T23:20:52Z")

Sample GetCoverage Request

New Mexico Resource Geographic Information System PRISM Precipitation Normals WCS Service. Live Link

http://gstore.unm.edu/apps/rgis/datasets/2ce10b57-3925-4971-b876-b6fc66d3cca2/services/ogc/wcs?
    SERVICE=wcs&
    REQUEST=GetCoverage&
    VERSION=1.1.2&
    COVERAGE=us_ppt_1971_2000_11&
    CRS=urn:ogc:def:crs:EPSG::4326&
    BBOX=24.0625,-125.02083333333,49.93749998965,-66.47916669008&
    FORMAT=image/tiff&
    WIDTH=2048&
    HEIGHT=905